1. Field of the Invention
The present invention relates to a safety belt. More particularly, the invention relates to a safety belt for racing cars and rally sports cars which include two shoulder belts and a lap belt which can be coupled to the shoulder belts by means of a buckle. The belts are at least indirectly fastened to the car frame.
2. Description of the Prior Art
Safety belts with four, five or six anchoring points are known. These safety belts are used primarily in racing cars, rally cars or sports cars. Generally, the safety belts consist of two shoulder belts, a lap belt and in some cases even two thigh belts.
The particularly shaped structure of such safety belts has the purpose to ensure optimum immobilization of the driver of the car during the competition.
By means of safety belts of the above-described type, each part of the body of the driver is firmly and symmetrically pressed against the backrest of the seat. For this purpose, the belt has two shoulder belts which extend over the shoulders and at least one so-called lap belt which surrounds and holds the lap or pelvis of the driver.
However, it has been found that the driver is insufficiently secured by means of the above-described safety belts. This insufficient securing of the driver is due to various dynamic phenomena which were determined in crash tests of a test vehicle with an antropomorphic, instrumented dummy.
The crash tests were carried out in accordance with the requirements of EWG 77/541 for impacts at 50 km/h and a braking curve.
The most apparent difficulties and disadvantages which were determined as a result of the above-mentioned test method in the known safety belts are as follows:
1. The so-called submarining phenomenon which means that the lap belt slides from its known position over the pelvic ridge and is displaced onto the soft portions of the abdomen. As a result, the danger of serious injuries in the area of the abdomen (kidneys, liver, bowels, spleen) exists.
2. It has been found that the resulting acceleration at the chest may be 60 g and more, which is to be considered the maximum permissible value in accordance with U.S. standard 208.
3. Another negative phenomenon occurring in the use of the known safety belts is that the permissible maximum limit of the head injury criteria value (HIC) is exceeded. This HIC value is determined in accordance with U.S. standard 208 as shown below and is fixed at 1000. ##EQU1##
The above value has been recognized in the international standards as a valid value for testing the protective system for the user of the belt.
The HIC value is reached by the head at the time of impact when the head is violently jolted forwardly as the sternum forcibly hits the safety belt and when the head is simultaneously turned downwardly, so that the value resulting at the chest exceeds the permissible maximum value of 60 g.
Moreover, it has been found that the symmetric forward displacement of the upper body, i.e. chest, arms and head, during the impact is a result of the fact that the kinetic energy E of the body at the time of impact is divided into two equal portions E.sub.1 and E.sub.2 which are absorbed and dissipated by the two shoulder belts of the known safety belts over equal time periods t.sub.1 and t.sub.2. Thus, the shoulders are displaced forwardly in a symmetrical manner.
The above-described difficulties and disadvantages result from the above-mentioned symmetrical displacement in conjunction with a low elongating or stretching capability of the safety belts.
Of course, if safety belts with thigh belts are used, the submarining phenomenon can be eliminated by means of the thigh belts. However, the risk of injuries to the groin in case of impact are substantially increased.
Even when safety belts with five or six anchoring points and with thigh belts are used, the above-mentioned 60 g value at the chest and the 1000 HIC is frequently easily exceeded.
It is, therefore, the primary object of the present invention to provide a safety belt in which the disadvantages and difficulties of known safety belts resulting from the uniform displacement of the body during an impact are eliminated.